上顎第二大臼歯抜歯後の上顎第三大臼歯の萌出に影響を及ぼす因子

Factors influencing the successful eruption of the maxillary third molar after extraction of the maxillary second molar.

抄録

はじめに:

本研究では、上顎第二大臼歯抜歯後に自然萌出した上顎第三大臼歯の咬合状態を評価し、上顎第三大臼歯の咬合状態に影響を及ぼす因子を検討した。

INTRODUCTION: This study evaluated the occlusal status of the maxillary third molars that erupted spontaneously after extraction of the maxillary second molars and investigated the factors that influenced the occlusal status of the maxillary third molars.

方法:

87名の患者の136本の上顎第三大臼歯を評価した。アライメント、マージナルリッジの不一致、咬合接触、近心間接触、頬側オーバージェットを用いて咬合状態をスコア化した。咬合状態は、上顎第3大臼歯の完全萌出時（T1）において、良好（G群）、可（A群）、不良（P群）に分類した。上顎第三大臼歯の萌出に影響する因子を明らかにするために、上顎第二大臼歯抜歯時（T0）とT1において、ノーラステージ、長軸角、上顎第三大臼歯の垂直・水平位置、上顎結節腔を評価した。

METHODS: We assessed 136 maxillary third molars in 87 patients. Alignment, marginal ridge discrepancy, occlusal contact, interproximal contact, and buccal overjet were used to score the occlusal status. Occlusal status was classified as good (G group), acceptable (A group), and poor (P group) for the maxillary third molar at its full eruption (T1). The Nolla's stage, long axis angle, the vertical and horizontal position of the maxillary third molar, and the maxillary tuberosity space were assessed at the time of maxillary second molar extraction (T0) and T1 to identify factors influencing the eruption of the maxillary third molar.

結果:

G群47.8％、A群17.6％、P群34.6％であった。年齢はT0、T1ともにG群で最も低かった。T1における上顎結節腔と上顎結節腔の変化量はG群で最も大きかった。T0におけるNolla's stageの分布には有意差があった。G群ではステージ4が60.0％、ステージ5、6が46.8％、ステージ7が70.4％、ステージ8〜10が15.0％であった。多重ロジスティック回帰分析によると、T0時の上顎第3大臼歯のステージ8-10と上顎結節の変化量はG群と負の相関があった。

RESULTS: G, A, and P groups comprised 47.8%, 17.6,% and 34.6% of the sample, respectively. Age was the lowest in the G group at both T0 and T1. The maxillary tuberosity space at T1 and the amount of the change of maxillary tuberosity space were the largest in the G group. There was a significant difference in the distribution of the Nolla's stage at T0. The proportions of the G group were 60.0% in stage 4, 46.8% in stages 5 and 6, 70.4% in stage 7, and 15.0% in stages 8-10. According to multiple logistic regression analysis, stages 8-10 for the maxillary third molar at T0 and the amount of the change of maxillary tuberosity were negatively associated with the G group.

結論:

上顎第二大臼歯抜歯後、上顎第三大臼歯の65.4％に良好～許容範囲の咬合が認められた。上顎結節腔の増大が不十分で、T0時のNolla stageが8以上であることは、上顎第三大臼歯の萌出に悪影響を与えた。

CONCLUSIONS: Good-to-acceptable occlusion was seen in 65.4% of the maxillary third molars after maxillary second molar extraction. Insufficient increase in the maxillary tuberosity space and Nolla stage 8 or higher at T0 negatively influenced the maxillary third molar eruption.